Though the Early Modern Philosophers are known for their skepticism of the external world, several philosophers of this time attempted to argue against this skepticism such as Thomas Reid and Immanuel Kant. René Descartes himself even asked colleagues for their objections to the techniques he employed, demonstrating the serious weight given to external world skepticism. To the objection that he merely re-raised the Platonic doubt of one's senses Descartes replies that he did not intend to pass his writing off as new, but rather to preemptively firm up his method (creating a fairly sturdy straw man, in fact) in anticipation of proving even that method incapable of shaking his metaphysics.
Thomas Reid
(26 April 1710 – 7 October 1796)
I. On forming opinions
II. Theory of Ideas
III.
It is important to note the respect Reid pays to Descartes. Marking the distinction between "old" and "new" philosophy, Descartes signaled the transition from the way of analogy to the way of reflection. The former, while an adequate tool in common life and study, is overly-simplistic, and allows the layman to draw (at best) loose and (at worst) false conceptions of intangible and intractable objects. The seafaring man will, for example, view his search through truth in the same with which he would take in the sea and navigation. The way of reflection, however, leads more optimistically to truth:
It may be observed that the method which Descartes pursued naturally led him to attend more to the operations of the mind by accurate reflection and to trust less to analogical reasoning...Intending to build a system upon a new foundation, he began with a resolution to admit nothing but what was absolutely certain and evident...It was not in the way of analogy but of attentive reflection that he was led to observe that thought, volition, remembrance, and the other attributes of the mind are altogether unlike extension [and]...they ought to make us diffident and jealous of every notion concerning the mind and its operations which is drawn from sensible objects in the way of analogy and to make us rely only upon accurate reflection as the source of all real knowledge upon this subject. (Inquiry)
The way of reflection leads to truth, but it is very difficult and seldom practiced even by philosophers. Analogy may be easy, but if someone has more direct evidence they should always pursue that line of thought.
Reid's central attack was on the Theory of Ideas: the claim that the immediate objects of perception are ideas in the mind rather than objects outside of the mind. The focus of Reid's attack rested on the his claim that the root of skepticism lay in this theory:
But what if these profound disquisitions into the first principles of human nature, do naturally and necessarily plunge a man into this abyss of skepticism? May we not reasonably judge so from what hath happened? Descartes no sooner began to dig in this mind, than skepticism was ready to break in upon him. He did what he could to shut it out. Malebranche and Locke, who dug deeper, found the difficulty of keeping out this enemy still to increase; but they laboured honestly in the design. Then Berkeley, who carried on the work, despairing of securing all, bethought himself of an expedient: By giving up the material world, which he thought might be spared without loss, and even with advantage, he hoped by an impregnable partition to secure the world of spirits. But, alas! the
Treatise of human nature wantonly sapped the foundation of this partition, and drowned all in one universal deluge.
These facts, which are undeniable, do indeed give reason to apprehend, that Des Cartes’s system of the human understanding, which I shall beg leave to call
the ideal system, and which, with some improvements made by later writers, is now generally received, hath some original defect; that this skepticism is inlaid in it, and reared along with it; and, therefore, that we must lay it open to the foundation, and examine the materials, before we can expect to raise any solid and useful fabric of knowledge on this subject. (Inquiry 1.VII)
One of Reid's arguments against Descartes' skepticism was that by following his reasoning one arrives at the conclusion that ideas have no existence except when we think about them. No thoughts can permanently exist. The body, which is an idea we sense, that Descartes wants to believe in is necessarily made non-existent because it cannot permanently exist. Furthermore, a flaw in this "new system" is that is allows the assumption of thought, sensation and consciousness as first principles from which to reason everything else out, and thereby does not employ complete doubt; Descartes and Locke thus grow lazy, stopping short of the end of skepticism "for want of light to carry them farther." Reid says,
"Either these things (the body, spirit, cause, effect, time and space) are ideas of sensation or reflection or they are not; if they are ideas of sensation or reflection, they can have no existence but when we are conscious of them; if they are not ideas of sensation or reflection, they are words without any meaning." (Inquiry 1.III)
Reid says that Descartes did not think of this consequence, which uproots his reasoning entirely. Additionally, the "new system" inevitably borrows more than it intends from the "way of analogy," and thus the argument arrives nowhere new.
He generated several more arguments against the theory of ideas, including a "practical knowledge" objection and the "stand or fall" response.
Practical Knowledge Response:
According to Reid, a clear defect of skepticism is the inability of man to live as if skepticism were true:
It is a bold philosophy that rejects, without ceremony, principles which irresistibly govern the belief and the conduct of allmankind in the common concerns of life; and to which the philosopher himself must yield, after he imagines he hathconfuted them. (Inquiry 1.VI)
Stand or Fall Objection:
Reid found particular fault with the Rationalism of Descartes and Malebranch who eschewed the veracity of the senses for that of reason when both faculties were created by a good, non-deceiving God.
The sceptic asks me, Why do you believe the existence of the external object which you perceive.
This belief, Sir, is none of my manufacture; it came from the mint of Nature; it bears her image and superscription; and, if itis not right, the fault is not mine: I even took it upon trust, and without suspicion.
Reason, says the sceptic, is the only judge of truth, and you ought to throw off every opinion and every belief that is not grounded on reason.
Why, Sir, should I believe the faculty of reason more than that of perception; they came both out of the same shop, and were made by the same artist; and if he puts one piece of false ware into my hands, what should hinder him from puttinganother? (Inquiry 6,XX)
Immanuel Kant
(22 April 1724 – 12 February 1804)
The "Refutation of Idealism" is Kant's criticism of the theory that "declares the existence of objects in space outside us either to be merely doubtful and unprovable or to be false and impossible." He is directly responding to Descartes problematic idealism that asserts only that "I am" and Berkeley's dogmatic idealism that declares space an impossibility. (Critique B274)
Kant's argument lays claim both to the view that the external world is external only insofar as it is a permanent thing that does not change when the perceiver changes and that perception requires the flow of time which itself is a permanent thing. "The proof it demands must,therefore, establish that external things we have not merely imagination but also experience."(Critique B775) So, perception must be of things external to the perceiver.
Thomas Reid
(26 April 1710 – 7 October 1796)
I. On forming opinions
II. Theory of Ideas
III.
It is important to note the respect Reid pays to Descartes. Marking the distinction between "old" and "new" philosophy, Descartes signaled the transition from the way of analogy to the way of reflection. The former, while an adequate tool in common life and study, is overly-simplistic, and allows the layman to draw (at best) loose and (at worst) false conceptions of intangible and intractable objects. The seafaring man will, for example, view his search through truth in the same with which he would take in the sea and navigation. The way of reflection, however, leads more optimistically to truth:
It may be observed that the method which Descartes pursued naturally led him to attend more to the operations of the mind by accurate reflection and to trust less to analogical reasoning...Intending to build a system upon a new foundation, he began with a resolution to admit nothing but what was absolutely certain and evident...It was not in the way of analogy but of attentive reflection that he was led to observe that thought, volition, remembrance, and the other attributes of the mind are altogether unlike extension [and]...they ought to make us diffident and jealous of every notion concerning the mind and its operations which is drawn from sensible objects in the way of analogy and to make us rely only upon accurate reflection as the source of all real knowledge upon this subject. (Inquiry)
The way of reflection leads to truth, but it is very difficult and seldom practiced even by philosophers. Analogy may be easy, but if someone has more direct evidence they should always pursue that line of thought.
Reid's central attack was on the Theory of Ideas: the claim that the immediate objects of perception are ideas in the mind rather than objects outside of the mind. The focus of Reid's attack rested on the his claim that the root of skepticism lay in this theory:
But what if these profound disquisitions into the first principles of human nature, do naturally and necessarily plunge a man into this abyss of skepticism? May we not reasonably judge so from what hath happened? Descartes no sooner began to dig in this mind, than skepticism was ready to break in upon him. He did what he could to shut it out. Malebranche and Locke, who dug deeper, found the difficulty of keeping out this enemy still to increase; but they laboured honestly in the design. Then Berkeley, who carried on the work, despairing of securing all, bethought himself of an expedient: By giving up the material world, which he thought might be spared without loss, and even with advantage, he hoped by an impregnable partition to secure the world of spirits. But, alas! the
Treatise of human nature wantonly sapped the foundation of this partition, and drowned all in one universal deluge.
These facts, which are undeniable, do indeed give reason to apprehend, that Des Cartes’s system of the human understanding, which I shall beg leave to call
the ideal system, and which, with some improvements made by later writers, is now generally received, hath some original defect; that this skepticism is inlaid in it, and reared along with it; and, therefore, that we must lay it open to the foundation, and examine the materials, before we can expect to raise any solid and useful fabric of knowledge on this subject. (Inquiry 1.VII)
One of Reid's arguments against Descartes' skepticism was that by following his reasoning one arrives at the conclusion that ideas have no existence except when we think about them. No thoughts can permanently exist. The body, which is an idea we sense, that Descartes wants to believe in is necessarily made non-existent because it cannot permanently exist. Furthermore, a flaw in this "new system" is that is allows the assumption of thought, sensation and consciousness as first principles from which to reason everything else out, and thereby does not employ complete doubt; Descartes and Locke thus grow lazy, stopping short of the end of skepticism "for want of light to carry them farther." Reid says,
"Either these things (the body, spirit, cause, effect, time and space) are ideas of sensation or reflection or they are not; if they are ideas of sensation or reflection, they can have no existence but when we are conscious of them; if they are not ideas of sensation or reflection, they are words without any meaning." (Inquiry 1.III)
Reid says that Descartes did not think of this consequence, which uproots his reasoning entirely. Additionally, the "new system" inevitably borrows more than it intends from the "way of analogy," and thus the argument arrives nowhere new.
He generated several more arguments against the theory of ideas, including a "practical knowledge" objection and the "stand or fall" response.
Practical Knowledge Response:
According to Reid, a clear defect of skepticism is the inability of man to live as if skepticism were true:It is a bold philosophy that rejects, without ceremony, principles which irresistibly govern the belief and the conduct of all mankind in the common concerns of life; and to which the philosopher himself must yield, after he imagines he hath confuted them. (Inquiry 1.VI)
Stand or Fall Objection:
Reid found particular fault with the Rationalism of Descartes and Malebranch who eschewed the veracity of the senses for that of reason when both faculties were created by a good, non-deceiving God.The sceptic asks me, Why do you believe the existence of the external object which you perceive.
This belief, Sir, is none of my manufacture; it came from the mint of Nature; it bears her image and superscription; and, if it is not right, the fault is not mine: I even took it upon trust, and without suspicion.
Reason, says the sceptic, is the only judge of truth, and you ought to throw off every opinion and every belief that is not
grounded on reason.
Why, Sir, should I believe the faculty of reason more than that of perception; they came both out of the same shop, and
were made by the same artist; and if he puts one piece of false ware into my hands, what should hinder him from putting another? (Inquiry 6,XX)
Immanuel Kant
(22 April 1724 – 12 February 1804)
The "Refutation of Idealism" is Kant's criticism of the theory that "declares the existence of objects in space outside us either to be merely doubtful and unprovable or to be false and impossible." He is directly responding to Descartes problematic idealism that asserts only that "I am" and Berkeley's dogmatic idealism that declares space an impossibility. (Critique B274)
Kant's argument lays claim both to the view that the external world is external only insofar as it is a permanent thing that does not change when the perceiver changes and that perception requires the flow of time which itself is a permanent thing. "The proof it demands must,therefore, establish that external things we have not merely imagination but also experience."(Critique B775) So, perception must be of things external to the perceiver.